datapath: Encapsulate parameters for new vports in new struct vport_parms.

datapath: Encapsulate parameters for new vports in new struct vport_parms.

Upcoming commits will keep needing to pass more information to the vport
'create' member function.  It's annoying to have to modify a dozen pieces
of code every time just to do this, so this commit encapsulates all of the
parameters in a new struct and passes that instead.

Acked-by: Jesse Gross <jesse@nicira.com>